So the difference between a theoretically pure prediction market and Kalshi is ... this interview? The CEO saying that he thinks others, who do not answer to him in any way, will be doing something to enforce some notion of fairness.

If you're being that puritan about the definition, then having a "real" prediction market is completely impossible. Because actors like the DOJ do not wait for a statement by the Kalshi CEO to bring charges. And rational actors will know and anticipate that, and hence preemptively comply. So you never get the unfettered version of a prediction market.

I don't think it makes sense to be that puritan about a definition that the thing it's trying to define becomes an impossibility. Polymarket, Kalshi et al are clearly prediction markets in the messy reality that we live in, and we're figuring out as we go what the legal reality of a real-world prediction market is and should be.